[BUGFIX] Remove invalid markup in SelectCheckBoxElement

Resolves: #104088
Releases: main
Change-Id: I22ed897cf9f320ddaa6a51fdb133c61df264af7d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84684


Reviewed-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Michael Telgkamp <michael.telgkamp@mindscreen.de>
Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Reviewed-by: Michael Telgkamp <michael.telgkamp@mindscreen.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>